Software tools for validating application performance can emulate hundreds or thousands of concurrent users by applying production workloads to an application platform or environment. The emulation puts the application through the rigors of real-life user loads while collecting information from key infrastructure components. Such application performance tools apply consistent, measurable, and repeatable loads to an application under test and then use resulting data to identify scalability issues that can affect real users. An application performance tool may include a virtual user generator that can run scripts to apply the loads to the application under test. To be useful, such scripts should accurately emulate the communication patterns that will be experienced by the application in production.